Cathode materials for secondary (rechargeable) lithium batteries

Abstract

The invention relates to materials for use as electrodes in an alkali-ion secondary (rechargeable) battery, particularly a lithium-ion battery. The invention provides transition-metal compounds having the ordered-olivine, a modified olivine, or the rhombohedral NASICON structure and the polyanion (PO 4 ) 3− as at least one constituent for use as electrode material for alkali-ion rechargeable batteries.

1 . A cathode material for a rechargeable electrochemical cell, said cell also comprising an anode and an electrolyte, the cathode material comprising a compound of the rhombohedral NASICON structure having the formula:  
         Li x M 1-(d+t+q+r) D d T t Q q R r (XO 4 )  
       wherein: 
 M is a cation of a metal selected from the group consisting of Fe, Mn, Co, Ti, Ni or mixtures thereof,  
 D is a metal in the +2 oxidation state selected from the group consisting of Mq 2+ , Ni 2+ , Co 2+ , Zn 2+ , Cu 2+ , and Ti 2+ ;  
 T is a metal in the +3 oxidation state selected from the group consisting of Al 3+ , Ti 3+ , Cr 3+ , Fe 3+ , Mn 3+ , Ga 3+ , Zn 3+ , and V 3+ ;  
 Q is a metal in the +4 oxidation state selected from the group consisting of Ti 4+ , Ge 4+ , Sn 4+ , and V 4+ ;  
 R is a metal in the +5 oxidation state selected from the group consisting of V 5+ , Nb 5+ , and Ta 5+ ;  
 X comprises Si, S, P, V or mixtures thereof;  
 0≦x≦1; and  
 0≦d, t, q, r≦1, where at least one of d, t, g, and r is not 0.  
 
     
     
         2 - 61 . (Cancelled).  
     
     
         62 . A secondary battery comprising an anode, a cathode and an electrolyte, said cathode comprising a rhombohedral NASICON compound as set forth in  claim 1 .  
     
     
         63 . The battery of  claim 62 , where M is further defined as being selected from the group consisting of Mn, Fe, Co, and Ni.  
     
     
         64 . The battery of  claim 62 , where M is further defined as being a combination of cations, at least one of said cations being selected from the group consisting Mn, Fe, Co, and Ni.  
     
     
         65 . The battery of  claim 63 , wherein M is FE 1-x Mn x  or Fe 1-x Ti x , where 0≦x≦1.  
     
     
         66 . The battery of  claim 62 , wherein the anode comprises a compound selected from the group consisting of a metallic lithium, a lithium alloy, a lithium-carbon intercalation compound, a lithium-transition metal mixed nitride of anifluorite and a lithium-titanium spinel having the formula Li 1+a+z Ti 2-a O 4  where 0≦a≦⅓ and 0≦z≦1-2a.  
     
     
         67 . The battery of  claim 66 , wherein said cathode further comprises a conductive additive.  
     
     
         68 . The battery of  claim 67 , wherein said conductive additive is carbon.  
     
     
         69 . The battery of  claim 66 , wherein said cathode further comprises a polymeric binder.  
     
     
         70 . The battery of  claim 69 , wherein said polymeric binder is selected from the group consisting of a homopolymer of tetrafluoroethylene, a copolymer of tetrafluoroethylene, an ethylene-propylene-diene terpolymer, a polyether, a polyester, a methylmethacrylate-based polymer, an acrylonitrile-based polymer, and a vinyldiene fluoride-based polymer.  
     
     
         71 . The battery of  claim 70 , wherein said polymeric binder is a polyether.  
     
     
         72 . The battery of  claim 71 , wherein said polyether further comprises a salt comprising Li +  cations.  
     
     
         73 . The battery of  claim 72 , wherein said polyether is crosslinked.  
     
     
         74 . The battery of  claim 69 , wherein said polymeric binder has an ionic conductivity of between about 10 −7  and about 10 −2  (Scm −1 ).  
     
     
         75 . The battery of  claim 72 , wherein said polymeric binder is swollen by an aprotic solvent.  
     
     
         76 . The battery of  claim 75 , wherein said aprotic solvent is selected from the group consisting of: ethylene carbonate, propylene carbonate, dimethylcarbonate, diethylcarbonate, methyl-ethylcarbonate, y-butyrolactone, a tetraalkylsulfamide, a dialkylether of an ethylene glycol having a molecular weight ≦2000.  
     
     
         77 . The battery of  claim 76 , wherein said aprotic solvent is a dialkylether of an ethylene glycol having a molecular weight ≦2000.  
     
     
         78 . The battery of  claim 77 , wherein said dialkylether comprises a mono-ethylene glycol.  
     
     
         79 . The battery of  claim 77 , wherein said dialkylether comprises a di-ethylene glycol.  
     
     
         80 . The battery of  claim 77 , wherein said dialkylether comprises a tri-ethylene glycol.  
     
     
         81 . The battery of  claim 77 , wherein said dialkylether comprises a tetra-ethylene glycol.  
     
     
         82 . The battery of  claim 77 , wherein said dialkylether comprises an oligo-ethylene glycol higher than a tetra-ethylene glycol.  
     
     
         83 . The battery of  claim 77 , wherein said dialkylether comprises a mixture of mono-, di-, tri-, tetra-, and higher oligo-ethylene glycols.